INTRACELLULAR CALCIUM OSCILLATIONS IN CELL-POPULATIONS OF RAS-TRANSFECTED I-7 SUBLINE OF HUMAN HACAT KERATINOCYTES

We have observed oscillations of intracellular Ca2+ (Ca-i) concentrati on in populations of rns-transfected HaCaT keratinocytes of I-7 sublin e. In postconfluent monolayers of I-7 keratinocytes, an increase in ex tracellular Ca2+ (Ca-o) concentration to 0.25-0.5 mM induced sinusoida l Ca-i oscillations, which persisted longer than 1 h with amplitudes o f 50-150 nM and periods of 5-10 min, Thapsigargin, which depletes inte rnal Ca2+ stores, did not prevent Ca-o-induced Ca-i oscillations, and it also induced Ca-i oscillations in the ras-transfected I-7 line, Rem oval of extracellular Ca2+ or addition of Ca2+-entry blocker La3+ or S K&F 96365 inhibited Ca-i oscillations, suggesting that Ca-i oscillatio ns in ras-transfected HaCaT keratinocytes were dependent on Ca2+ influ x across the plasma membrane, Because the Ca-o-induced Ca-i oscillatio ns have been observed only in rns-transfected I-7 subline and not in i ts nontransfected parental HaCaT line, this may provide a partial expl anation for the divergent responses of ras-transfected and nontransfec ted keratinocytes to Ca-o signal for control of growth and differentia tion.